A cross-sectional view of a milking machine teat cup of the type commonly used in the dairy industry is depicted in schematic form in FIG. 1, and is generally denoted by the reference numeral 100. The teat cup 100 includes a teat cup shell 102, which is usually made of a rigid material such as stainless steel or plastic, and which has a generally cylindrical teat cup interior surface 104 surrounding a pulsation chamber 106. The teat cup shell 102 extends between an open teat cup mouth 108 (through which a cow's teat is received as discussed below) and an open milk extraction end 110 (from which milk is extracted). The teat cup shell 102 also generally includes a pressure supply connection nipple 112 which opens onto the pulsation chamber 106 for purposes to be discussed below.
A teat cup liner 114, which is usually formed of rubber or another elastomeric substance, is then mounted under tension within the teat cup shell 102. The teat cup liner 114 has a liner mouth end 116 with a liner mouth 118 sized to receive the cow's teat. The liner mouth 118 opens onto a generally cylindrical liner interior 120, which is surrounded by the interior surface 122 of a barrel portion 124 of the liner 114. The exterior surface 126 of the liner barrel 124 is spaced from the teat cup interior surface 104. The liner barrel 124 radially constricts at the liner barrel exit 128, from which extends a narrower milk line 130 (which may be integrally connected to the barrel exit 128, and which may terminate at a juncture 132 for connection to a “claw” or other milk receiving vessel). It should be understood that the teat cup 100 is usually provided in a milking cluster with three additional teat cups 100, all of which are connected to the claw or other vessel.
During milking, the cow's teat is inserted into the liner mouth 118 to extend down the liner barrel 124. Negative pressure (i.e., a vacuum force) is applied to the liner interior 120 via the milk line 130, and also to the pulsation chamber 106 via the pressure supply connection nipple 112. Milk is thereby extracted from the teat owing to the pressure difference across the orifice of the cow's teat, and the milk is collected through the milk line 130. The pulsation chamber 106 is usually periodically opened to atmospheric pressure (generally about once per second) to cause the liner barrel 124 to collapse, thereby generating a massaging action on the teat from the contracting liner barrel 124. Further examples of teat cups of this nature, and further details on their operation, may be found (for example) in U.S. Pat. No. 6,427,624 to Briggs et al.; U.S. Pat. No. 6,588,364 to Petterson; and U.S. Pat. No. 6,722,310 to Alveby et al., among others.
Since the teat cup liner 114 will eventually wear and/or become unsanitary, it is provided as a removable/disposable component of the teat cup shell 102. For ease of fitting and removal within the teat cup shell 102, the teat cup liner 114 is often provided with a descending flange 134 about its mouth end 116 so that the flange 134 may fit about and affix to the teat cup mouth 108, with the liner milk line 130 fitting through the teat cup extraction end 110.
When using a typical milking machine which includes teat cups such as the teat cup 100, dairy producers are faced with the challenge of preventing the transmission of organisms that cause bovine mastitis, an inflammation of a cow's mammary glands. A mild case of mastitis in a cow can merely reduce milk production, while in a severe case, it may result in the death of the cow. Some of the organisms which cause mastitis are highly contagious, and are easily spread from cow to cow when a milking machine is transferred from one cow to another during milking. Thus, a mastitis outbreak can rapidly spread through a herd and devastate its milk production. One study has estimated the cost of mastitis in the United States to be approximately 6% of the value of milk production (Wells et al., “What Is the Current Milk Quality in the U.S.?,” 1998 National Mastitis Council Annual Meeting Proceedings).
Proper sanitation of milking machines is therefore critical to mastitis control. Milking machines are typically cleaned using hot water, detergents, and disinfectants two or three times per day, corresponding to the milking frequency of the herd, so that the machines will theoretically be free of the organisms that cause mastitis. However, since milking machines are rarely cleaned between milking individual cows, mastitis-causing organisms can be easily transferred between cows during a milking session. Devices which clean teat cups 100 between the milking of individual cows have been developed, the most common of which are “backflush” rinsing systems. These have not been widely adopted because they are expensive to install and maintain, and they require large amounts of water and disinfectants for operation. Additionally, they are not always effective in removing bacteria populations from the teat cup liner 114. As a result, it would be beneficial to have a more effective and economical means for quickly and easily disinfecting teat cup liners 114 between milking individual cows, with little or no use of disinfectants or other consumables.